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Anthropomorphic Phantoms Analytical and voxel models Status and perspectives. Giorgio Guerrieri July 13 th , 2005. Mathematical phantoms The size and shape of the body and its organs are described by mathematical expressions representing combinations and intersections of planes,

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anthropomorphic phantoms analytical and voxel models status and perspectives
Anthropomorphic PhantomsAnalytical and voxel models Status and perspectives

Giorgio Guerrieri July 13th, 2005

a wide panorama of phantoms

Mathematical phantoms

The size and shape of the body

and its organs are described

by mathematical expressions

representing combinations and

intersections of planes,

circular and elliptical cylinders

spheres, cones, tori, …

Voxel phantoms

Based on digital images

recorded

from scanning of real persons

by computer tomography (CT)

or

magnetic resonance imaging

(MRI).

NRPB Mathematical Phantom

(National Radiological Protection Board)

Gibbs Phantom

(1984)

NORMAN Phantom

(MRI data of a volunteer)

MIRD5 Phantom

(Medical Internal Radiation Dose Committee, pamphlet no 5)

Zubal Phantom

(from CT and MRI data)

ORNL Phantom

(Oak Ridge National Laboratory)

Missing in Geant4

Already developed by other group using Geant4, not public

A wide panorama of phantoms
slide3

Interest on Anthropomorphic Phantoms

2005, April: Monte Carlo Topical Meeting, Tennessee

In the session about “Tomographic Models for Radiation Protection Dosimetry”,

many talks about anthropomorphic phantom (mainly voxel-based models) have been presented:

- GSF Male And Female Adult Voxel Models Representing ICRP Reference Man By Keith Eckerman

- Effective Dose Ratios For The Tomographic Max And Fax Phantoms By Richard Kramer

- Reference Korean Human Models: Past, Present and Future By Choonsik Lee

- The UF Family of Paediatric Tomographic Models By Wesley Bolch and Choonik Lee

- Development And Anatomical Details Of Japanese Adult Male/ Female Voxel Models By T. Nagaoka

- Dose Calculation Using Japanese Voxel Phantoms For Diverse Exposures By Kimiaki Saito

- Stylized Versus Tomographic Models: An Experience On Anatomical Modelling At RPI By X. George Xu

- Use Of MCNP With Voxel-Based Image Data For Internal Dosimetry Applications By Michael Stabin

- Application Of Voxel Phantoms For Internal Dosimetry At IRSN Using A Dedicated Computational Tool

By Isabelle Aubineay-Laniece

- The Use Of Voxel-Based Human Phantoms In FLUKA By Larry Pinsky

- The Future Of Tomographic Modelling In Radiation Protection And Medicine (Panel discussion)

slide4

Anthropomorphic Phantoms for Geant4 toolkit

  • The representation of the human body is useful for radiation protection and medical physic simulation applications.

In particular for applications in radiation shielding of habitats

for astronauts, such as transfer vehicles and surface habitats

for future manned exploration missions.

The development of anthropomorphic phantoms, together with Geant4 physics

modelling, makes possible to study the radiation damage to the astronauts' organs during interplanetary missions.

  • The models of anthropomorphic phantoms can be used not only in space science, but also for cancer therapy studies too.
slide5

First Step

Analytical Phantom

DICOM interface

Voxel Phantom

Anthropomorphic Phantoms for Geant4 toolkit

The project for Geant4 toolkit is addressed to develop anthropomorphic phantom that can beentirelycustomized by the user.

As in URD, the user shall be able to:

- Choose model for each body part to add to the phantom (ORNL, MIRD)

- Add single voxel-based body part from DICOM file (CT, MRI)

analytical model

First attempts to model the shape of a human being and its internal organs in order to calculate absorbed radiation doses were made by Snyder et al. (1969) and Koblinger (1972).

These were based on the anthropomorphic MIRD-type phantom, which was originally developed for the dosimetry of internal radionuclide sources.

The Medical Internal Radiation Dose Committee creates MIRD5

that has been the basis for various derivations, like the ORNL Mathematical Phantom Series.

W. S. Snyder, M. R. Ford, G. G. Warner, H. L. Fisher jr

MIRD Pamphlet # 5 Revised: “Estimates of absorbed fraction for monoenergetic photon sources uniformly distributed in various organs of a heterogeneous phantom”, J Nucl Med Suppl 3, 1969.

K. F. Eckerman, M. Cristy, J. C. Ryman

“The ORNL Mathematical Phantom Series”, http://homer.ornl.gov/vlab/VLabPhan.html

Analytical Model

The anatomies of new-born, and children of age 1 year, 5 year, 10 year, 15 year and adult male and female had been modelled at the Oak Ridge National Laboratory by Cristy and Eckerman (1987).

modelling with geometries

Sketch of the gastrointestinal

tract model

Skeletal system

An example of how MIRD5 describes brain

Exterior of the phantom

Brain

Modelling with geometries
final result

The sizes and the positions of geometrical

representations of body parts are taken

from the document:

ORNL Mathematical Phantom Series

From ORNL Series: model of trunk as elliptical cylinder

This document allows to create different

phantoms choosing its age and sex.

Back view

Front view

“Final” result
anthropomorphic phantom urd 1

Body regions

Trunk, neck, head, legs, male genitalia, breasts

Skeletal systemLeg bones, arm bones, pelvis, spine, skull, rib cage, clavicles, scapulae

Gastrointestinal tract and contentsEsophagus (thoracic + abdominal portions),stomach (wall + contents), small intestine, upper large intestine (ascending colon wall and contents, transverse colon wall and contents), lower large intestine (descending colon wall and contents, lower large sigmoid colon wall and contents)

Heart and contents

Outer surface of heart, left ventricle (wall + contents), right ventricle (wall + contents),

left atrium (wall + contents), right atrium (wall + contents), heart (wall + contents)

Organs

Adrenals, brain, gall bladder (wall + contents), kidney, liver, lung,ovary, pancreas, spleen, testes, thymus, lobes of thyroid, urinary bladder (wall + contents), uterus

Anthropomorphic Phantom: URD (1)

- The goal of the project is the development of a Geant4 package addressed to the modelingof an anthropomorphic phantom providing a realistic description of the human body and anatomy.

- The phantom consists of a mathematical model of:

slide10

Anthropomorphic Phantom: URD (2)

Elemental composition of tissues:

  • The user shall be able to define composition of each tissue
  • The user shall be able to associate a defined material to each part of phantom

Event:

  • The user shall be able to retrieve the position and material of the body region traversed by tracks

User interface:

  • The user shall be able to select a phantom by the sex, the age, the model
  • The user shall be able to construct a phantom using single parts from different models by choosing among MIRD, ORNL or Voxel (from CT/MRI DICOM data)
  • The user shall be able to add sensitivity to specific organs
  • The user shall be able to create specific body region corresponding to subset of the phantom

Visualization:

  • The user shall be able to visualize the geometrical set-up
  • The user shall be able to visualize the particle tracks
slide11

Anthropomorphic Phantom: Design

  • The anthopomorphic phantom will be implemented exploiting the object oriented technology
  • A rigorous software process is adopted.
  • The object oriented technology allows extensive code reuse, flexibility, easy extension of the software.
slide12

Abstract Factory

  • The design pattern Abstract Factory is adopted to define anatomic structures.
  • The user can model organs communicating with the abstract interface G4VBodyFactory, independently from their concrete classes.

The Abstract Factory

provides an interface

for creating families

of related object

without specifying

their concrete classes.

It makes exchanging

product families easy.

It can use different product

configurations simply

by changing the concrete factory.

slide13

Builder

The creational pattern Builder separates the construction of a complex object from its representation

so that the same construction process can create different representations.

The Builder object provides the director

with an abstract interface for constructing

the product.

Thanks to the abstract interface

G4VPhantomBuilder,

all one has to do to change the product's

internal representation is define

a new kind of builder.

Unlike creational patterns that construct

products in one shot,

the Builder pattern constructs the product

step by step under the director's control.

problems

In both ORNL and MIRD mathematical phantoms most of the organs can be easily approximated

with solids or part of them that currently are not implemented in the Geant4 Geometry Package:

  • Ellipsoid
  • Circular and elliptical oblique cone
  • Elliptical cone
  • Torus with elliptical section
Problems …
g4ellipsoid

Geant4 functionality has to be extended, developing the software to describe the ellipsoid

Design of the new

class G4Ellipsoid

G4Ellipsoid

The ellipsoid

and part of it are used to describe several organs like stomach, ovaries, brain, or lungs and kidneys...

1 dimensional test
1-Dimensional Test

This test consisted of 1D-flux of geantinos with direction parallel to X axis impinging onto an ellipsoid.

The ellipsoid has semi-axis lengths: a = 7. µm , b = 10. µm, c = 15. µm.

The solid is spaced in an enclosed box volume defined world which sizes are 40.µm.

The number of events generated in the test is 10^4.

The same test was performed for 1D-beams with direction parallel to Y and Z directions.

The path length of the geantinos was verified to be equal to the sizes of the ellipsoid, as expected.

Path Length

2 dimensional test
2-Dimensional Test

This test consisted of an isotropic flux of geantinos impinging onto an ellipsoid.

The ellipsoid has semi-axis lengths: a = 7. µm, b = 10. µm, c = 15. µm.

The solid is spaced in an enclosed box volume defined world which sizes are 40 µm.

The number of the events generated in the test is 5 ·10^5.

Projection on plane XY, YZ, ZX

g4ellipsoid18

Ellipsoid cut by two planes along the Z-axis

The software implementing the ellipsoid has been included in

Geant4 CVS repository in Geometry/solids/specifics.

This work will be documented by an INFN pre-print (in progress)

G4Ellipsoid

The new class G4Ellipsoid

is meant to be publicly available

in the next Geant4 release.

gdml geometry description markup language

Solids

CSG solids:

- box

- tube

- cone

- sphere

- parallelepiped

- trapezoid

- general trapezoid

Boolean solids:

- union

- subtraction

- intersection

Materials

Materials definitions

- isotopes

- elements

- elements built from

isotopes

- complex materials

- molecules

- mixtures built from

elements and/or other

complex materials

by fractional mass

Numerical expressions

Actual definitions of

numerical elements:

- constant

- quantity

- expression

- Cartesian position and

rotation

GDML Geometry Description Markup Language

The Geometry Description Markup Language work-package is meant to provide geometry data exchange format for the LCG applications.

The work-package consists of the GDML Schema part, which is a fully self-consistent definition of the GDML syntax, and the GDML I/O part, which provides means for writing out and reading in GDML files.

What users gain is the reduced time when writing their geometry description as no need for re-compilation and re-linking of their applications is required even for one number change.

The other advantage is that it allows them easy exchange of geometry data without a need to reveal their source code and makes life easier for developers as well because they can use the GDML data for tracing bugs and problems in geometry processing code.

The GDML work-package can be useful for simplify geometry description of body parts

slide20

The GDML work-package read out geometries implemented in Geant4. If other solids will be implemented (the ellipsoid...) in the Geant4 Geometry Package, the GDML Processor is to be extended with them.

  • Currently GDML can create volumes parametrized and replica only of boxes and tubes. [UR 1.2.10] The rib cage is represented by a series of bands between two concentric, right vertical, elliptical cylinder.

Problems …

slide21

The GDML Schema has been extended with the new solid, the ellipsoid,

and the GDML Processor is now able to draw ellipsoid.

The next official GDML distribution will have

the extension to read the new solid

(once the G4Ellipsoid is available in G4 release)

http://simu.cvs.cern.ch/cgi-bin/simu.cgi/simu/GDML2/GDMLSchema/

The GDML package has been extended

to create volumes parametrized for the elliptical tube.

Extending GDML

slide22

Implementation of

an anthropomorphic phantom example

We have explored GDML functionality for a preliminary implementation

of an example of an analytical anthropomorphic phantom.

Elements of “Human phantom” example:

  • Primary Particle
  • Geometry
  • Physics
  • Messengers
slide23

Definition of primary particle type, primary vertex

and momentum

Primary particle can be originated in different conditions

- The user can choose the type of particle

- The user can originate beam with defined energy and initial direction

- The user can originate particle from a sphere (isotropic flux)

Primary Particle

slide24

The Geometry is generated from a GDML file through GDML Processor

GDML file is created by the user, through User Interface.

- The user can choose phantom by sex (Male or Female)

- The user can choose phantom by model (ORNL, MIRD or MIX)

- The user can choose which body part is to be built

- The user can set sensitivity for each body part

Geometry

slide25

Materials

Materials are defined in GDML file

There are three materials defined for different body parts:

- Skeleton: for the parts of skeleton system

- Lung: for the lungs

- Soft Tissue: for all other body part

These are defined by their elemental composition and densities.

slide26

The body parts can be sensible volumes

In body part volume the energy deposit is collected

The energy deposit is given by the primary particles

and all the secondaries generated.

Sensitive Body Part

slide27

Geant4 phantom has messengers to control:

- Visualizations (OPENGL, VRML, DAWN)

- Primary Particles in term of initial energy and direction

- Geometry set-up

Messengers

slide28

<?xml version="1.0" encoding="UTF-8" ?>

<gdml xmlns:gdml="http://cern.ch/2001/Schemas/GDML" ...

<define>

(...)

</define>

<materials>

(...)

</materials>

<solids>

(...)

</solids>

<structure>

(...)

<volume name="BreastsVolume" >

<materialref ref="SoftTissue" />

<solidref ref=”BreastsVolume” />

</volume>

<volume name="BodyVolume" >

<materialref ref="SoftTissue" />

<solidref ref="Body" />

<physvol>

<volumeref ref="BrainORNLVolume" />

<positionref ref="BrainORNLPos" />

<rotationref ref="BrainORNLRot" />

</physvol>

(...)

</volume>

(...)

Through macro file adultFemale.mac

# Initialize Phantom

/phantom/startUserPhantom

# Define Sex

/phantom/setUserPhantomSex Female

# Define Model

/phantom/setUserPhantomModel ORNL

# Body part and Sensitivity

/bodypart/addBodyPart Stomach yes

/bodypart/addBodyPart Spleen no

/bodypart/addBodyPart Brain yes

...

# Finalize GDML file

/phantom/closeUserPhantom

Set sensitivity

GDML file is processed by GDML Processor

and the user phantom is built...

Example of geometry setup

slide30

Female ORNL Anthropomorphic Phantom

Skull

Spine

Thyroid

Esophagus

Lungs

Arm Bones

Breasts

Spleen

Heart

Pancreas

Stomach

Liver

Kidneys

Upper Large Intestine

Pelvis

Ovaries

Uterus

Lower Large Intestine

Urinary Bladder

Leg Bones

Not visible: Brain (in the skull)

slide31

TrackID: 2 -> LegBonesORNLVolume -> Energy deposit: 3.4576726 MeV

TrackID: 2 -> BodyVolume -> Energy deposit: 5.1323606 MeV

TrackID: 2 -> BodyVolume -> Energy deposit: 5.1711365 MeV

TrackID: 2 -> BodyVolume -> Energy deposit: 701.06096 keV

TrackID: 16 -> BodyVolume -> Energy deposit: 807.59738 keV

TrackID: 23 -> BodyVolume -> Energy deposit: 1.497982 keV

TrackID: 22 -> BodyVolume -> Energy deposit: 2.3391091 keV

TrackID: 21 -> BodyVolume -> Energy deposit: 220.25512 eV

TrackID: 20 -> BodyVolume -> Energy deposit: 10.468365 keV

TrackID: 19 -> LegBonesORNLVolume -> Energy deposit: 16.651015 keV

TrackID: 24 -> BodyVolume -> Energy deposit: 4.0614721 keV

Female ORNL Anthropomorphic Phantom> Run 1 <

Particle: gamma

Energy: 100. MeV

no. Particle: 20

Beam Direction: along Z axis

Visualization system: OpenGL

Output of run 1

slide32

TrackID: 19 -> ArmBonesORNLVolume -> Energy deposit: 2.148 keV

TrackID: 34 -> ArmBonesORNLVolume -> Energy deposit: 70.168538 keV

TrackID: 33 -> BodyVolume -> Energy deposit: 19.493675 keV

TrackID: 32 -> BodyVolume -> Energy deposit: 42.318809 keV

TrackID: 31 -> SpleenORNLVolume -> Energy deposit: 119.96815 keV

TrackID: 30 -> SpleenORNLVolume -> Energy deposit: 3.9230135 MeV

TrackID: 29 -> PancreasORNLVolume -> Energy deposit: 1.0284905 MeV

TrackID: 18 -> BodyVolume -> Energy deposit: 543.1 eV

TrackID: 37 -> BodyVolume -> Energy deposit: 33.841459 keV

TrackID: 36 -> LiverORNLVolume -> Energy deposit: 986.16275 eV

TrackID: 35 -> LiverORNLVolume -> Energy deposit: 1.9230902 keV

Female ORNL Anthropomorphic Phantom> Run 2 <

Particle: gamma

Energy: 100. MeV

no. Particle: 20

Beam Direction: along X axis

Visualization system: OpenGL

Output of run 2

conclusions

A first model of analytical anthropomorphic phantom

has been created for Geant4 simulation toolkit

Conclusions
  • A new solid ellipsoid has been designed, implemented and tested to extend the Geant4 geometry package.The solid enables the representations of many body parts.
  • GDML work-package has been extended and now it's able to read the ellipsoid from Geant4 geometry and to create volumes parametrized of elliptical tube.
  • GDMLwork-package seems to be useful to simplify the geometry description of the analytical anthropomorphic phantom.
future

Analytical Phantom

Organs

Customized Phantom

DICOM interface

Future
  • Development of a prototype of analytical anthropomorphic phantom to be used in simulation applications of radioprotection study or medical physics.
  • Allow user to build customized anthropomorphic phantom with organs described by analytical model and DICOM interfacecreating a voxel-analytical phantom.
anthropomorphic phantoms analytical and voxel models status and perspectives35
Anthropomorphic PhantomsAnalytical and voxel models Status and perspectives

Giorgio Guerrieri July 13th, 2005